Distance sensing apparatus

Abstract

Apparatus for sensing distances in air by transmitting an ultrasonic pulse and measuring the time for return of an echo from a target object is characterized by ability to measure distances to multiple target objects. Preferably the apparatus defaults by displaying the distance to the nearest target but is provided with a push button which when pressed once causes display of the distance to the next target further away, when pressed again causes display of distance to a target after that and so forth. This novel function may be accomplished by discrete logic components or using a microprocessor.

I claim: 
     
       1. An apparatus for measuring distances in air, comprising transmitter means to transmit at least one ultrasonic or sonic signal, echo detecting means to detect receipt of an echo of said signal, time sensing means which generates a numerical value proportional to time from transmission to return of an echo, and display means to display a digital distance measurement derived from said numerical value and which is a measure of distance to the target returning the echo, the improvement comprising ability to detect any one of at least two echoes returning in succession from different distances and within a range, and for any one of said echoes to generate a said numerical value and display a said digital distance measurement obtained therefrom, irrespective of the distances within said range from which the echoes return, means for regularly and automatically repeating the transmitted signal at sufficient delay for return of an echo from a maximum range, control means selectively operable to choose between said echoes returning in succession and to cause said time sensing means and display means respectively to generate a said numerical value and display a said digital distance measurement obtained therefrom, said control means being user operable to choose any one of said echoes, irrespective of the distances within said range from which the echoes return. 
     
     
       2. An apparatus for measuring distances in air, comprising transmitter means to transmit at least one ultrasonic or sonic signal, echo detecting means to detect receipt of an echo of said signal, time sensing means which generates a numerical value proportional to time from transmission to return of an echo, and display means to display a digital distance measurement derived from said numerical value and which is a measure of distance to the target returning the echo, the improvement comprising ability to detect any one of at least two echoes returning in succession from different distances and within a range, and for any one of said echoes to generate a said numerical value and display a said digital distance measurement obtained therefrom, irrespective of the distances within said range from which the echoes return, and control means selectively operable to choose between said echoes returning in succession and to cause said time sensing means and display means respectively to generate a said numerical value and display a said numerical distance measurement obtained therefrom, said control means being user operable to choose any one of said echoes, irrespective of the distances within said range from which the echoes return. 
     
     
       3. Apparatus according to claim 2 wherein said time sensing means act to determine a said numerical value associated with each of said echoes, and said control means are selectively operable to choose between said numerical values. 
     
     
       4. Apparatus according to claim 2 wherein said time sensing means comprises a counter which generates a numerical value proportional to time from transmission to return of an echo, the apparatus comprising means to average a plurality of said values obtained from repeated transmitted signals and echoes thereof. 
     
     
       5. Apparatus according to claim 2 wherein the control means is selectively operable to choose between three or more said echoes. 
     
     
       6. Apparatus according to claim 5 wherein said selectively operable control means is a push-button or a keyboard key having a single action, said control means being operable repeatedly with an incremental action, such that operation while one of said echoes is currently chosen serves to choose the one of said echoes returning from the next greater distance. 
     
     
       7. Apparatus according to claim 2 wherein said means to detect receipt of an echo produces an electrical signal in response to each echo of a single transmitted signal, provided these echoes have sufficient amplitude and return from sufficiently different distances within said range, said control means being operable to choose between the said signals produced and cause said time sensing means to generate a said numerical value for the said echo chosen by operation of said control means.   
     
     
       8. Apparatus according to claim 7 wherein, when the chosen echo is other than the first one of the said echoes of a transmitted signal, the said signal corresponding to the echo preceding the chosen echo enables response by the time sensing means to the subsequent said signal corresponding to the chosen echo. 
     
     
       9. Apparatus according to claim 8 wherein said time sensing means comprises a counter for clock pulses, and said apparatus includes circuit means for transmitting said signal corresponding to the chosen echo to stop said counter, the said signal corresponding to the preceding echo enabling said circuit means to transmit said signal corresponding to the chosen echo. 
     
     
       10. Apparatus according to claim 7 comprising a microprocessor with an interrupt input, said signals corresponding to echoes being supplied to said interrupt input. 
     
     
       11. Apparatus according to claim 10 wherein said time sensing means comprises a counter for clock pulses, which counter is separate from said microprocessor, said apparatus including circuit means for transmitting said signal corresponding to the chosen echo so as to stop said counter, said microprocessor being controlled by a stored program such that when the chosen echo is other than the first echo, said microprocessor counts interrupts created by each of the said signals corresponding to echoes, and upon interrupt by the signal corresponding to the echo before the chosen echo, enables said circuit means to transmit said signal corresponding to the chosen echo. 
     
     
       12. Apparatus according to claim 2 having a definite state in which the chosen echo is the first echo of sufficient amplitude returning from between minimum and maximum distances, the apparatus going to said definite state when switched on and/or when reset, 
     
     
       13. Apparatus according to claim 2 comprising means for regularly and automatically repeating the transmitted signal after sufficient delay for return of an echo from a maximum range. 
     
     
       14. Apparatus according to claim 13 wherein the apparatus is operable to detect at least one echo of a first transmitted signal, then to pass over any echoes of a subsequent transmitted signal, which echoes return from within the same distance as said at least one echo of the first transmitted signal, and generate a said numerical value for a following echo of said subsequent transmitted signal and display a digital distance measurement derived therefrom. 
     
     
       15. Apparatus according to claim 2 wherein the apparatus is operable to detect at least one of the echoes of a transmitted signal, then to detect a following echo of the same transmitted signal, generate a said numerical value for said following echo and display a digital distance measurement obtained therefrom. 
     
     
       16. Apparatus according to claim 2 possessing ability to detect three or more said echoes returning in succession, and for any one thereof generate a said numerical value and display a said digital distance measurement.